Method for heat sealing the seams of paper bags



Nov. 16, 1948. A. M. BOJANOWER 2,453,839-

METHOD FOR HEAf-SEALING THE SEAMS OF PAPER BAGS Filed March 7, 1944 fl l'lu'l lllll \/VENTUR ALEE'R TM EUMQWER Patented Nov. 16, 1948 METHOD FOR HEAT SEALING THE SEAMS OF PAPER BAGS 1 Albert M. Bojanower, Downey, Calif., assignor to v Western Waxed Paper Company,

Oakland,

Calif., a corporation of California Application March 7, 1944, Serial No. 525,430

2 Claims. (Cl. 154-116) This invention relates to bags, wrappers. or other containers made from paper in which there are seams formed by overlapping plies or edges of the paper adapted to be secured together by heat-softenable adhesive. More particularly this invention relatesrto the sealing of overlapping plies of such material as waxed paper, sheets coated with nitro-ceilulose or other solvent coated sheets, pliofllm, etc., and applies to the heat sealing of the same in which the application of heat, by softening or melting the adhesive or coating on the opposing sheet surfaces causes them to adhere firmly together. This invention relates especially to heat treatment by which water soluble adhesives, as well as adhesives mixed with other solvents, can be made to adhere to waxed paper or other coated sheets.

The usual method of applying heat for such purposes or of sealing the seams of overlapping edges of waxed paper and the like is to pass these edges or plies over or under a heated element or between heated elements so arranged as to produce heat and pressure along the seam, as, for example, passing the overlapping edges between heated rollers, etc; The rollers or other heated metal elements are customarily heated either by steam or by electric heating means.

However, since the heated metal is brought into direct contact with the paper at the seam and also presses against the paper, I have found that considerable difficulty is frequently encountered in forming a properly sealed seam. Considerable care must be taken with such sealing means to control the heat of the metal, for if the metal is allowed to become too hot the paper with which it is brought into contact becomes brittle and dry even though the paper may not actually be scorched. Furthermore the overheating of the wax, and any adhesive which may be mixed with the wax, causes this to be spread out too thin,

and overheating may also impair thequality of.

the adhesive. As a result of such factors I have observed that failures along waxed paper seams are of common occurrence.

The object of this invention is to prevent the occurrence of these failures in the heat-sealing of the paper seams by performing the sealing in such manner that actual contact of the paper with any heated metal surfaces will be avoided.

I have discovered further that the application of steam itself directly to the .paper at the seam, instead of the application of metal heated by the steam, for the purpose of softening the wax or coating and any adhesive mixed with it, produces very satisfactory results and avoids the possibility of failures of the seam referred to above.

A further object of this invention, therefore, is

. 2 i to provide an improved method of sealing such paper seams which will involve the direct application of steam to the paper for producing the required heating of the overlapping plies.

The manner in which my invention may be carried out and a preferred means which I have found successful in accomplishing my purpose will be described with reference to the accompanying drawings in which:

Fig. 1 is a view in isometric prospective of my improved steam seam heater, with a portion of the outer shell of the main steam chamber broken away; and I Fig. 2 is an illustration of a waxed paper bag, drawn to smaller scale, indicating seams formed in accordance with my invention.

The device shownin Fig. 1 includes a steam container or chamber A having an outer cylindrical shell ill and a jet block B connected to the steam chamber and firmly attached to the cylindrical shell Ill. The Jet block B has a channel ii (shown in broken line) extending longitudinally through the center of the block, the ends of the channel being sealed or plugged. The bottom of the block 13 is drilled with a plurality of small holes I! which connect with the central channel II and constitute outlets for the channel ii.

A supporting bracket I 3 has its upper end secured to the cylindrical shell Ill. The block B is rigidly secured to the lower end of bracket 63. The top of the block B is drilled and tapped to receive the end of the pipe I! which connects with the steam chamber A. Steam enters at the other end of the chamber 'A through the pipe is which is connected to any suitable source of, steam supply (not shown).

A central core i8 extends through the chamber A and the steam entering the chamber A through the pipe I! passes between the core l8 and the inside of-the outer wall or shell Ill. The core I6 is adapted to have a removable electric heating element or cartridge ll inserted in the core whenever it is desired to superheat the steam passingas nozzles for the steam Jets. 4 The paper bag is passed underneath the block B. but spaced a short distance from the bottom surface of the block' and supported by any suitable means, and is .so positioned during its movement past the block same.

assasae that the jets of steam from the holes or nozzles II will strike the bag along the steam which isto be heat sealed. The heat from the steam jets softens the wax or other coating of the paper at the seam, and also softens any adhesive which may have been mixed with the wax or coating be tween the overlapping plies, causing the overlapping plies or'edges to adhere together as the seam is then pressed down. for example by passing the bag between press rollers, (which are not shown), which press rollers are not. heated. Should there be more than one seam, for instance a bag bottom seem as well as a longitudinal seam. the bottom seam is subjected similarly tomcat treatment by the steam jets and pressure is then applied to the seams during the cooling of the Fig. 2 illustrates a common type of waxed paper bag C having alongitudinal seam l8, formed by the overlapping plies or edges of the waxed paper, and a folded-over bottom seam is, both of which seams have been subjected to heat treatment from the steam jets and have had pressure applied for a short period during the cooling of the seams.

with the employment oi,my method of heat sealing the seam of the paper there is less likelihood of burning the paper as it moves past the heater or of causing the paper to become brittle by the heat. n the contrary, the application of steam from the steam jets directly to the paper adds a small amount of moisture to the top ply of the paper along the seam thus tending to make the paper even more soft and pliable during the heat treatment. Similarly when adhesive is mixed with the wax or other coating on the opposing faces of the overlapping plies of paper the direct application of steam reduces the danger of such adhesive becoming too brittle as the result of the heat transfer. For these reasons I prefer to employ steam, in carrying out my method of heat transfer, instead of other-hot gasses, although my invention can also be carried out with the latter as well.

Furthermore it will be obvious that any spreading of the seam, which is apt to occur when the seam is subjected to pressure under heated metal elements, is avoided by my method since the paper does not contact the surface of the block B. The application of pressure to the paper along the seam would take place during the cooling of the seam and consequently there is no killing of the seam by excessive spreading out of the wax or other coating and-of the adhesive which may be mixed with it between the overlapping plies.

The steam jets, striking the paper a short distance from the jet block 3, result in a concentration of the heat in a narrow path 'along the seam as the bag is moved beneath the block and consequently there is a greater concentration of heat transferred and a more efllcient heat transfer. As a result of this more efficient transfer of heat the sealing of the bags can be performed more rapidly than is customary when the bags are obliged to be brought into direct contact with metal elements which are heated and .which spread the heat. and the steam jets enable heat from a large heat generating equipment, regardless of the location of such equipment, to be utilized and applied exactly as desired.

while I have found that the use of ordinary steam in accordance with my invention is sufdalso found that superheating the steam applied to the seam. higher temperature of the steam discharged )5 heat sealing of 55 plies of waxed paper,

in II the jets, which higher temperature is possible by superheating the steam before discharging, results in a, more rapid heating of the seam brought into contact with the jets and enables the operation 5 to be performed at higher speed. The superheating of the steam also eliminates the possibility of any actual water liquid being discharged from the nozzles with the steam jets. At ordinary steam temperature occasional drops of water will be discharged in the jets and while this is not a serious objection, nevertheless it is not desirable to have actual water deposited on the paper.

while I have referred in this description primarily to the employment of my invention in the seams in waxed paper bags it would, as previously indicated, be possible to use my method for applying heat to seams in bags and the like made of other kinds of paper where the coating or the heat-softenable adhesive, either no separately or in combination, serves as the medium between the overlapping plies for holding the seam together. However, I consider the most important use of my invention to be with ordinary waxed paper bags, particularly since 3 failures in the seams of such bags have become such a generally recognized problem.

Various modifications could be made in the device which I have illustrated and described for carrying out my invention, and changes in thesuperheater, jet block, etc., might be made. The particular device which I have shown is merely one means by which my invention may be carried out but I have found this particular device by actual experiment and practise to be very satisfactory.-

1. The improved method of heat-sealing a seam in a paper bag formed by two overlapping plies of waxed paper, which method includes heating the paper along the seam by means of a small jet of steam injected downwardly against the upper face of the upper overlapping ply, restricting the heating of the paper to the direct contact of the steam jet with the paper and keeping the paper from actual contact with any heated solid object wax between the plies, and finally pressing the overlapping plies together with unheated pressing means while the seam is cooling.

2. The improved method of heat-sealing a seam in a waxed paper bag formed by two overlapping which method includes applying a heat-softenable adhesive along one of the opposing faces of the overlapping plies, heating the paper along the seam by means of a. plurality of small alined jets of steam ejected co downwardly against the upper face of the upper overlapping ply, restricting the heating of the paper to the direct contact of the steam jets with the paper and keeping the paper from actual contact with any heated solid object in order to avoid excessive heating of the paper and spreading or "killing of the adhesive or wax in the seam, whereby the heat from the steam jets passing through the upper overlapping ply will soften the adhesive and wax between the two piles, and

finally pressing the overlapping plies together with unheated pressing means while the seam is cooling. ALBERT M. BOJANOWER.

' (References on following W 5 REFERENCES CITED Number The following references are of recordin the file of th1s patent: 2,293,568 UNITED STATES PATENTS 5 2,322,298 Number Name Date 2358325 2,084,625 Stebbins et a1 June 22, 1937 336717. 5 2,103,945 Henley Dec. 28, 1937 2372-737 6 Name Date Piazza May 9, 1939 Young July 14, 1942 Snyder Aug, 18, 1942 Johnston June 22, 1943 Hallman Sept. 19, 1944 Lindh et a1 Jan. 23, 1945 Phillips, Jr Apr. 3, 1945 

